Electric system



Oct. 16, 1951 R. H. amas 2,571,164

ELECTRIC SYSTEM Filed May 5, 1948 2 Sheets-Sheet l Aitomg Filed May 5, 1948 2 Sheets-Sheet 2 PULSE @u 4 LZ1/enter.' 2025527 H 22M/fs MM @y Aiorngy Patented Oct. 16, 1951 UNITED STATES PATENT OFFICE Original application February 18, 1946, Serial No. 648,482. Divided and this application May 5, 1948, Serial No. 25,241

(Cl. Z50-30) 9 Claims.

The present invention relates to electric systems, and more particularly to radio-receiving systems that, while having more general elds of usefulness, are especially adapted for use in television. The present application is filed in response to a requirement for division in application, Serial No. 648,482, filed February 18, 1946.

An object of the invention is to provide a new and improved radio-receiving system.

Another object is to provide a new and improved electret.

A further object is to provide a novel electret element that is adapted to receive and rectify radio Waves.

Other and further objects will be explained hereinafter and will be more particularly pointed out in the appended claims.

The invention will now be more fully explained in connection with the accompanying drawings, in which Fig. 1 is a diagrammatic view of circuits and apparatus arranged for radio-location purposes; Fig. 2 is a view of a modification; Fig. 3 is a diagram showing an airplane object from which radio waves are reflected and scattered to the receiving system of Fig. 1; and Fig. 4 is a view of a further modication.

An electromagnetic-wave generator 4 is shown exciting a dipole 2 to produce ultra-high-frequency pulsed-radio energy, say, of 3 or 1.5 centimeters wavelength. A continuous-wave or any other type of modulated-wave generator may be employed, but pulsed energy, at present, has the advantage of economical and easy high-power ultra-high-frequency generation.

The waves emitted by the dipole 2 may be directed by a reflector 3 upon a parabolic reflector 6. The parabolic reilector 6 is shown directing the waves toward an object, say, an airplane 8, from which they are reflected and scattered t- Ward a receiving station.

At the receiving station, the radio waves thus reflected and scattered from the object 8 may be focused by an electromagnetic dielectric lens 5, such as polystyrene, upon a bank or array 'I comprising a plurality of normally ineiective radioreceiving pick-up unit antenna elements. The dielectric lens may be replaced by any other type of well-known lens, such, for example, as a Wave-guide lens, mirror or other directive system for focusing the electro-magnetic energy scattered and reflected from the object 8 on the bank or array 'I of pick-up elements.

The pick-up elements of the bank or array 'I are shown arranged in the form `of rows :and columns, in the proximity of the focal plane yof viewing screen the lens 5. The first or uppermost row of the bank is illustrated as comprising the sections IU, I2, I4, I6, etc., shown as equally spaced hori- Zontally. The second row from the top is shown comprising the sections I 8, 28, 22, etc. The third or next-lower row is shown comprising the sections 24, 2B, etc., and so on for the remaining rows of pick-up elements. Though only a small number of pick-up units is shown in each row, this is merely for illustrative purposes, in order not to confuse the disclosure. It will be understood that, in practice, a large number of pick-up units will be employed in each row, say, 180.

The sections I 8, I8, 24, etc., are arranged in the iirst or right-hand column. The sections I2, `20, 26, etc., are disposed in the second column from the right. The sections I4, 22, ete., are disposed in the third column from the right, and so on. There may be as many columns as there are pick-up units in each row. Though each column is shown as comprising only a few pickup units, this is again in order not to complicate the drawings.

The pick-up units will, of course, all receive the reflected or scattered radio waves through the lens 5 simultaneously. There will be focused on each pick-up unit a radio-frequency voltage corresponding to the scattering from a corresponding view of the object 8. The pick-up elements will thus receive diierent field strengths of radio energy, corresponding to the amount of energy reflected or scattered from the various parts of the object 8 and converged upon the array 'I of pick-up elements by the lens 5. A radio-energy picture of the object 8, as will be presently explained, is thus recorded upon the array, specific elemental areas of which will correspond to specific elemental areas of the object 8. By means of the present invention, this radio-energy picture may be converted into a visible picture |23. According to the preferred embodiment of the invention, the visible picture |23 is caused to appear upon the fluorescent I 06 of a display cathode-ray oscilloscope tube 90. Though the tube 90, and also the hereinafter-described cathode-ray oscilloscope-like member 89, are shown operating on the electrostatic principle, magnetic deflection or a combination of magnetic and electrostatic forces may be employed. The invention provides a means for producing upon the screen IDB images corresponding to the radio-frequency energy received by the pick-up elements.

Provision is lmade for rst rendering the normally ineifective pick-up units I0, I2, I4, IB, etc., of the rst row successively effective momentarily in the display circuits; for then rendering the pick-up units I3, 2U, 22, etc., of the second row successively eiective momentarily; for then rendering the pick-up units 24, 26, etc., of the third row successively effective momentarily; and

so on.

The pick-up units are shown arranged in an insulating disc 9 at the screen end of the oscilloscope-like member 89, and the pick-up units may be constituted of electrets.

An electret is a permanently charged dielectric formed by iilling the gap between two electrodes with, for example, molten resin, carnauba wax, or beeswax, and subjecting the electrodes to high voltage. By allowing the wax to cool during the application of the high Voltage, a solidified permanently charged electric dipole is produced, having permanent piezo-electric properties. Investigations in this eld are described, for example, by A. Gemant in the Philosophical Magazine, S. '7, vol. 20, No. 136, Suppl. November 1935, pages 929 to 952.

- As described by W. G. Cady in Piezoelectricity, McGraw-Hill, page 235, mixtures of the resin or carnauba wax with other dielectric substances have produced long-lasting electrets. It will presently be explained that if these dielectric bases are combined in the same manner with radioabsorbing-and-rectifying materials, such as silicon or uranium oxide, the electrets can be particularly well adapted to the purposes of the present invention. One of the electrodes of the electret, furthermore, may serve to enhance the response to radio energy if, for example, it is tuned to the radio waves, such as if it is onequarter of a wave-length long.

The pick-up units previously described may be such electrets. The first row of units is shown composed of charged dielectrics I9, I2, I4, I9, etc., provided with top electrodes IIO, II2, II4, II 6, etc., respectively, and a common strip 43. The second row of units similarly is shown comprised of charged dielectrics I8, 20, 22, etc., provided with top electrodes IIB, I29, |22, etc., and a common strip 5I connected to the strip 43. Similarly the third row is shown composed of charged dielectrics 24, 26, etc., with top electrodes 29, IZB, etc., and a common terminal strip 51 connected to the other common strips 43, and 5I. The strips 93, 5I and 51 are shown connected by a conductor I8 to a grounded impedance 58, in the inout circuit of an amplifier 19.

The cathode-ray-oscilloscope-like member 89 is shown provided with a cathode 95, a controlgrid electrode 93 and an anode 91. Electrons emitted from the cathode 95 will become enabled, in response to proper stimulation of the grid 93, to pass by the grid 93 to the anode 9i of the member 89. The electrons will continue to travel in a stream from the anode 91, between a pair of vertically disposed deflector plates 99 and I0 I, of which the plate 99 is shown grounded, and between a pair of horizontally disposed deflector plates |93 and I95, of which the plate I95 is shown grounded, to impinge finally on the disc 9 of the member 89. A horizontal-sweeptime base, applied, as hereinafter more fully explained, to the vertically disposed deflector plates 99 and IBI, will cause the electron stream from the cathode 95 to become deiected horizontally, and a vertical-sweep-time base, applied to the horizontally disposed deflector plates |93 and I 95, will cause the electron stream to become deflected vertically. The rows of electret pick-up units may be positioned along the successive paths of the electron stream to enable the stream to impinge on them as it successively sweeps out the successive rows of the array 1.

If, accordingly, the lens 5 is caused to focus the radio-energy picture on the oscilloscope-like member 89, the bank of electrets will act to absorb the incident radio-frequency energy. The absorbed radio-frequency energy will alter the initial permanent polarizing static charge or voltage with which the electrets become sensitized during their preparation. This alteration results from several factors, including heating or pyroelectric effects, the negative temperature coeiiicients of resistance and the piezo-electric properties of the electrets. Silicon and uraniumoxide detectors are known to absorb radio-frequency energy and to exhibit negative temperature coeicients of resistance.

The energy absorbed by each electret is a measure of the intensity of the radio-frequency energy impinged thereon.

Across the electrodes of each electret, moreover, the radio-frequency energy will become rectified to produce direct-current potential diii'erences. These potential diierences are representative of the radio-frequency energy impressed on the tcp tuned electrodes of the electrets in the radioreceiving circuits comprising these tuned electrodes, the detecting electrets and the grounded conductor 18. The rectification is produced by the detecting dielectric disposed between the electret electrodes. The variation of potential and charge along the bank of electrets is thus a measure of the radio-frequency energy impinged on the array by the lens 5.

The resistance of the silicon or uranium oxide, as well as of the wax of the electret, since their temperature coeicients are negative, changes with the intensity of the impinging radio-frequency energy. A resistance variation is thus produced along the bank of electrets that is representative of the radio-frequency energy received by the respective electrets.

These three effects involving the change of the electret charge upon the absorption by the electrets of the radio-frequency energy, the production of the direct-current potentials as a result of the detection or rectification in the abovementioned radio-receiving circuits, and the resistance changes render the electret construction to which the present application is particularly directed extremely sensitive. With such electrets used for the particular illustrative radio-wavelocation purpose above described, a radio-energy image of the object 8 becomes thus recorded upon the array of electrets as charge, potential and resistance distributions.

The bank of electrets may be scanned according to either of two principles or according to a combination of the same. One principle involves measuring the variation in the electric charge and potential of the bank at the moment that the electron stream impinges upon the successively disposed electrets to short-circuit them. The other principle involves measuring in a grounded preferably linear amplier 'I9 the current along the electron stream as it impinges upon areas of dierent potential of the variously resistive electrets, completing the circuit to the ground through the successive electrets by way of the conductor 18.

Each electret will absorb and rectify the radiofrequency energy. Dependent -upon the magnitudofithisenergy, itiwill changethe resistance and: theA charge of the electret.v This change will result both as a consequence oft the-absorption and of therectifying actionfby.l the. electrets ofthe radio-frequency energy received` by the electret electrodes. As the electron stream successively impinges upon the successivelyV disposed electrets, during.r the scanning, it successively discharges them, This produces a corresponding change inthe input voltage tothe amplifier '|9, indicative of the radio-frequency energy impinged on the respective electrodes.

The electron stream Will` instantaneously discharge each differently-charged andv differentlypotentaled electret to give an indication in the load 58 and the amplifier 19, or it will give rise to a change in the electron-beam current when it impinges upon the variously resistive electret elements, or there may be a combination of these effects.

The scanning of the electrets may obviously also operate on the principle of change in electron-beam current transmitted to the load 58 upon impinging on surfaces of various resistances. As the stream hits these electrets of different resistances, a change in beam current occurs, which manifests itself in the input circuit of the amplifier 19.

Mosaics of electrets for the member 89 may also taken the form of Fig, 2, where electrets 8|, 84, 86, 88 are provided with front electrodes |8|, |84, |86, |88 exposed to the radio energy converged by the lens 5. The electrode strips |8|, |84, |86, |88 may be of length one-quarter of the wave-length of the radio waves and may be in the interior of the tube 89, facing the electron stream, and may be scanned by it. The electrodes 28|, 204, 286, '288 will' be capacitively coupled to the front electrodes and will assume the homocharge of the electret. Thus, the electron stream will impinge on surfaces of different charge or potential, and the scanning will take `place according to the principles previously described.

The electrets may be separated from adjacent electrets by dielectricmaterial 200.

As the electron stream produced from the cathode 95, in response to appropriate horizontalsweep-time-base voltages applied to the vertically disposed deflector plates 99 and |0| of the cathode-ray-tube-like member 89, travels across the pick-up elements in the disc 9, theyv will' successively discharge into the grounded preferably linear amplifier 19, by way of the conductor 18. If desired, the amplifier 'I0 may bek replaced by a bank of linear amplifiers, one corresponding to each of the pick-up elements.

The output of the amplifier "I0 will. obviously vary, at successive instants, in accordance with the radio-frequency energy received by the successive corresponding pick-up elements.

A. pulse generator, which may, if desired, be the same pulse generator 4, may be employed to trigger a horizontal-time-base-sweep circuit 53 and a vertical-sweep circuit |59, according to conventional and well-known television technique. The pulse generator 4 may feed, through an attenuator and rectifier to an oscillator or any similar or equivalent television circuit. One such circuit is shown as a pulse-recurrence-frequency multiplier 95, for applying many pulses corresponding to each radio-frequency pulse for the period between successive radio pulses, to trigger the horizontal-sweep circuit 63. The horizontal-time-base sweep will thereby be produced between the vertically disposed defiector plates 99 and |0|, occurring as many times, say, between successive radio-frequency transmissions, as there are rows of pick-up antennas. The pulse generator 4 may also feed, through theA attenuator and rectifier to trigger the vertical-sweep circuit 69, once corresponding to every radio-frequency transmission. One vertical sweep will then occur between the horizontally disposed plates |03, |05 during the periods between successive radio pulse transmissions, corresponding to as many horizontal sweeps as there are rows of antennas, causing each of the horizontal sweeps to appear at successively lower levels on the oscilloscope-sweep face.

If the circuit 95 comprises an oscillator, the oscillations may be employed to trigger the horizontal sweep. The period of the oscillations which, as previously explained., is much less than the duration of each radio pulse, corresponds to the time of sweep across one row of the pickup units in the disc 9.

If, as previously mentioned, continuous-wavev radio transmission is employed, the verticalsweep circuit G9 may be triggered to produce one vertical sweep corresponding to as many horizontal sweeps from the horizontal-sweep circuit 63 as there are rows of pick-up units.

Means is provided for producing upon the screen |96 of the display oscilloscope 90, images corresponding to the radio-frequency energy received by the corresponding pick-up mosaic antenna elements. The screen |06 is illuminated by an electron stream in the oscilloscope 90.. This electron stream is synchronized to travel with the electron stream of the cathode-raylike member 89. ,The horizontal-sweep circuit `|33 is, connected to the horizcntal-deflector plate |90 of the oscilloscope 99 by a conductor 6.1, and to the horizontal-deflector plate |0| of the oscilloscope-like member 89 by the conductor 61 and a conductor |34. The vertical-sweep circuit 69 is connected to the vertical-deflector plate |02 of the oscilloscope 90 by a conductor 1|, and to the vertical-deflector plate |03 of the oscilloscope-like member 89 by the conductor 1| and a conductor |46.

The amplifier 19 is connected, by conductors and 8l, to the control-grid electrode 92 and the cathode 94 of the oscilloscope 99. The mosaic of electrets becomes thus successively connected, through the amplifier 19, to the control electrode 92; Electrons emitted from the cathode 94 will become enabled, in response to the action of the amplifier '.'9, to pass by the grid 92, to the anode. 96 of the oscilloscope tube 90, The electrons will continue to travel in a stream from the anode 96, between the pair of vertically disposed oscilloscope defiector plates 98 and |00, of which the plate 98 is shown grounded, and between the pair of horizontally disposed oscilloscope deflector plates |02 and |04, of which the plate |04 is shown grounded, to impinge Iinal- 1y on the uorescent viewing screen |06 of the oscilloscope 90.

After each simultaneous horizontal sweep of both the oscilloscope 90, and the oscilloscope-like member 89 has been completed, a successively larger voltage will be applied to the horizontally disposed deflector plates |02, |04, and |03, |05, respectively, by the vertical-sweep circuit. After the last such horizontal sweep, the voltage between the horizontally disposed plates |02, |04 and |03, |05 will become restored to zero. The

Wheatstone construction.

next horizontal sweep, therefore, will start again at the first or top row.

Successively disposed areas of the screen 106 of the oscilloscope 90 will therefore correspond to the similarly disposed mosaic-antenna sections in the disc 9 of the member 69. Each spot along a particular horizontal sweep, therefore, will become brightened on the screen |06 according to the amount of radio energy received by the corresponding pick-up element, and fed, by way of the amplifier "i9, to the control electrode 92 of the cathode-ray oscilloscope 90.

A more sensitive video signal device might be any well-known vbridge detector of, say, the If the electrets are connected in a direct-current series circuit, then the bank of condenser electrets may serve as an extremely sensitive radio-detecting element of a Wheatstone bridge, in which they may be balanced against iixed impedance elements 212, 214 and 2 I6, as shown in Fig. 4. The short-circuiting or exploring of each successive electret by the electron stream, diagrammatically shown as shorting switches 265, 261, 209, in parallel with the electrets 204, 206, 208, would thus be markedly indicated in the amplifier 19 and fed to the control electrode 92 of the display oscilloscope 90.

Although the invention has been described in connection with mosaic-antennas arranged in rows and columns, it will be understood that this is not essential, for other arrangements are also possible. Antennas arranged along concentric zcircles covering the field, or a continuous spiral, will also serve, though the oscilloscope arrangement would, of course, be correspondingly modi' ed. In the case of the concentric circles and the spiral, the antennas would be rendered effective in two-dimensional order, as in the case of the rows and columns before described. The antennas disposed along one of the circles, for example, would iirst be rendered effective, then those along the next circle, and so on.

Further modifications will occur to persons skilled in the art, and all such are considered to fall within the spirit and scope of the invention, as deiined in the appended claims.

What is claimed is:

1. An electret element having, in combination, two spaced electrodes and a polarized wax base containing a radio-wave absorber-and-rectier inserted between the two electrodes.

2. An element of the character described comprising two spaced electrodes between which is disposed a permanently charged dielectric base combined with a radio-wave absorber-and-rectiiier.

3. Apparatus of the character described comprising an antenna connected to a permanently charged dielectric base combined with a radio-1 wave absorber-and-rectier.

4. A permanently charged element comprising two spaced electrodes between which is disposed a combination of a solidified polarized wax base and silicon.

5. A permanently charged element comprising two spaced electrodes between which is disposed a combination of a solidiiied polarized wax base and uranium oxide. l

6. A permanently charged element comprising two spaced electrodes between which is disposed a combination of a solidiiied polarized wax base, silicon and uranium oxide.

7. A permanently charged element comprising two spaced electrodes between which is disposed a combination of a solidified polarized dielectric base selected from the group consisting of resin, carnauba wax and beeswax and a radio-wave absorber.

8. A permanently charged element comprising two spaced electrodes between which is disposed a combination of a solidiiied wax base selected from the group consisting of resin, carnauba wax and beeswax and radio-wave absorbing material selected from the group consisting of silicon and uranium oxide.

9. An electret element having, in combination, polarized wax and a radio-wave detecting material and provided with an electrode tuned to the frequency of the radio waves.

ROBERT H. RINES.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,886,234 Meissner Nov. 1, 1932 1,969,379 Meissner Aug. 7, 1934 1,997,263 Meissner Apr. 9, 1935 2,024,705 Rutherford Dec. 17, 1935 2,046,476 Meissner July 7, 1936 2,267,954 Schumacher Dec. 30, 1941 2,429,823 Kinman et al Oct. 28, 1947 2,438,892 Becker Apr. 6, 1948 2,460,109 Southworth Jan. 25, 1949 OTHER REFERENCES Gemant: Recent Investigations on Electrets, Phil. Mag., S. 7, vol. 20, No. 135, Suppl. Nov. 1935, pages 929-952.

Padgett: Electret Behavoir, Radio-Electronics, page 32, May 1949.

Uutra-High Frequency Techniques by Brainerd et al., Van Nostrand Company, 1942, page 487. 

